Horticulture Guy

Q. I have two Japanese pear trees, don’t know the particular variety, but they have borne fruit over past years in abundance. However, last year I only find, that together, they only bore four pears.  Are others having the same thing happening in this area or is my experience a rare or odd event? Oscar Burlison - Tacoma, WA

                                                                                                        
A. What you are experiencing is something called “alternate bearing” or sometimes “biennial bearing”.  The majority of fruit and nut trees express some degree of this cyclical cropping pattern.  There is actually an alternate bearing index that grades cultivars based on their propensity to bear more heavily on alternating years. This shows that there are genetic factors that contribute to this pattern.  What happens physiologically in a fruit or nut tree is that a very heavy crop in one year depletes the carbohydrate reserves of the tree.  This carbohydrate reserve is the energy surplus that left at the end of the growing season, which is stored as carbohydrates in the root system.  This is the difference between the energy reserves from the year before added to the energy absorbed by the leaves during the season and the energy usage from growth, repair and reproduction.  An example of carbohydrate storage that most of us are familiar with is the Sugar Maple.  This is where real maple syrup comes from. In the fall surplus carbohydrates are stored in the roots. In the spring the carbohydrates are mobilized and converted from complex carbohydrates to simple carbohydrates like sucrose.  If you were to harvest too much sap in the spring the tree’s production would decline and the tree could eventually die.  Fruit trees have hormonal feedback systems that kick in when the carbohydrate levels drop below a threshold.  The result is fruit abortion.  The reason the tree seems to flower just as well in the weak year is because the flower buds are being formed early in the season for the next year long before the plant assesses its carbohydrate status.  What you can do is thin the fruits of your tree this year so that you even out production.  Thinning early is better since less energy goes into the fruit that will be removed.  About 2-3 weeks after blooming is ideal.  Remove fruit that are closer than 6 inches away from one another on the same branch.  If you have a strong alternate bearing tree then you will need to thin each year to keep it on an even keel.  Some other benefits of thinning are larger individual fruit as well as of branch breaking due to fruit load.

-- HG

Q. How tall will Prunus Caroliniana ‘bright and tight’ grow?  Will these shrubs grow as vigorously in a wine barrel container? Jamie Jameson - Monterey, CA

A. The Carolina Laurel Cherry is an evergreen tree/shrub that is native to the east coast from North Carolina over to Texas. This variety has a more compact habit than the species as the cultivar name suggests.  In the size container you suggest they probably will top out at 10 feet tall.  If they were grown in the ground they may reach 20 feet (The species can get as large as 40 feet tall).  I am sure you can grow them in California in pots but here in the Puget Sound region you would need to protect the plants during the winter.  These trees are rated to USDA Hardiness Zone 8, which would overwinter here in the ground.  When grown in containers I usually suggest buffering 2 zones.  So here in our Zone 8 areas I would suggest growing Zone 6 plants in containers when they are not protected during the winter.  Protection could be as simple as moving them to an unheated garage or in a protected area near the house.

-- HG

Q. Our back yard is landscaped with mostly rhodies, azaleas, Japanese maples and a variety of other acid loving plants.  The whole area is covered with bark.  The problem is that water seems to have a hard time penetrating the bark. Often after watering I will check the moisture and the soil beneath the bark will hardly be wet.  The plants are suffering from lack of water.  How can I improve this situation? Mardell Rediske - Puyallup, WA

                                                                                                        
A. The most likely cause for this situation is that the mulch is to thick and/or to fine textured.  When the proper mulch is applied at the proper thickness it will allow water as well as air penetration to the roots below (roots breath oxygen too!) while simultaneously moderate soil temperature, reduce the impact of irrigation and raindrop impact, reduce evaporation of soil moisture and suppress weed seed germination.  It is one of the foibles of human nature to think that if a little is good then more is better.  But if mulch is applied too thickly water and air exchange will be compromised.  Coarse mulch has more space between the mulch particles and therefore will allow for better water penetration and air circulation than finer particle mulch.  Mulch should be from two to four inches thick to work effectively. Coarse mulch can be applied at the higher end of the range and fine mulch at the lower end of the range.  Mulch is reapplied each year to replace that which is lost each year due to decomposition.  So what can also happen is that mulch is reapplied without testing the depth of the existing mulch.  After a few seasons the mulch depth is too deep.  If you find that your mulch depth is ideal then not enough water is being applied.  Use a water can or rain gauge to measure the amount of water being applied.  One inch per week is usually sufficient.    

-- HG

Q. We recently purchased a chipper/shredder and have disposed of many branches from fir trees this way.  I noticed that leaving it in a pile, it gets very hot and turns to like ash within a week, in the center of the pile.  If I spread it over my garden, it turns to like a beauty bark color, and doesn’t get hot after a week or two.  Can I use this as a mulch, and do I need to use it after it turns to ash like, or just let it sit on the garden?  Do I need to put anything else in the soil when I use it?  Thanks, Midge Patten - Allyn, WA

A. The reason the pile gets hot and changes consistency so fast is because the green needles and the brown wood shredded together supply the ideal ratio of carbon (brown) and nitrogen (green) for the aerobic (oxygen using) decomposing microorganisms.  The act of shredding also provides more surface area for the decomposers to work on.  Although it is not critical to allow the mulch to decompose for a week if you like the more uniform consistency of the product then by all means use it.  You do not need to add anything to the soil since the mulch sits on top of the soil and will only use nitrogen from the very surface of the soil leaving the nitrogen below available for the plants’ roots.  As I mentioned to Mardell be sure to apply it at the proper thickness.  So if you have shredded it very fine two inches will be enough.  If it is fairly coarse then you can go up to four inches. 

-- HG

Q. I would like to create some artificial “Growth zones” for some bonsai trees. I would like to create a zone 7. How would I go about doing this and what kinds of artificial lights would I need? Charley Stran - Eau Claire, WI
A. To create a true zone 7 inside a home can be difficult especially if you are growing deciduous bonsai specimens.  The USDA zones really only concern themselves with the lowest minimum temperatures.  But the zone still has cold temperatures and daylength changes that are necessary in the proper amounts to trigger dormancy and then to break dormancy. You may be able to achieve this in an unheated garage and use a light timer to change the day length to match outdoors resetting it once weekly to follow the seasons. The grow lights could be as simple as fluorescent full spectrum bulbs (or one warm white and one cool white bulb) or as sophisticated as metal halide lamps.  If you are using an unheated garage you may need no additional heat but you should be sure that the temperature doesn’t go below 10 degrees F, which is the upper threshold for zone 7.   Many bonsai enthusiasts have outdoor hotbeds, which are essentially cold frames with heating cables on the bottom.  Most deciduous specimens will need a specific dormancy period where the temperature is between freezing and 45 degrees F.  If you can provide that you can grow most deciduous plants.  Don’t forget plants have a range of zones that they can grow in.  They will have a lower limit zone and an upper limit zone.  The lower limit zone is usually based on the coldest temperature it can tolerate.  The upper zone has to do with how warm the winters are and dormancy.  This is why Florida grows citrus and not peaches or apples.  It is to warm in the winter and the peaches and apples don’t break dormancy. 

-- HG

Q. Hi Peter. I enjoy your column very much.  My frustrations with being surrounded by neighbors with invasive tree roots, noxious ivy and raspberry runners is only surmounted by the larger question: what to do with all of the rocks that are displaced when planting? Though I agree in principle with the idea of not bringing in “foreign” soil, as a fellow Lakewood resident, you must realize that for every bucket of soil there are three bushels of big round rocks. We do sift, and have been rather creative about using as many rocks as possible, but we are running out of room. Do you have any suggestions for how to find out about some solutions for this problem? Who might need this type of fill, or where can they be dumped? I really hate to go out to prepare any more planting areas because I know there will be another mountain of rocks sitting there and I just don’t know what to do with them anymore. Thanks for listening. Judy Cross - Lakewood, WA

A. Although my yard does have plenty of “gravel” I have not run into that many big round rocks.  The deposits in my part of town tend toward the medium to small.  Because of the glacial origin of our soil there can be quite a bit of variation even within town limits.  Also as I have mentioned in previous columns in addition to the glacial history of your yard’s soil you also have the more recent history of its development when your home was built and the potential redistribution of topsoil.  So you may dealing with a very shallow topsoil profile and having to dig into areas of soil with lot’s of what my Dad would euphemistically call “potatoes”. The best thing to do in this situation is to set up raised beds in your new garden areas.  They can be as simple as wooden timbers, bricks or cinderblocks or as elaborate as low curved retaining walls.  This allows you to use some of the native soil but not have to dig too deeply and be greeted by bushels of big rock. Six to twelve inches of depth is best for a raised bed.  So you may be wondering what you should fill the bed with if you don’t wish to bring in topsoil.  I prefer to only add organic matter and mix it with the existing soil.  Products like Cedar Grove Compost (http://www.cedar-grove.com) are great for making raised beds.  Just be sure to mix some of the existing soil into the compost to make sure there are soil minerals available to the plants.  If you really have no existing topsoil to work with then use either their Vegetable Garden Mix which is equal parts screened sandy loam, Cedar Grove compost screened to 7/16″ and sand or their Two-Way Topsoil 50% Cedar Grove Compost screened to 7/16″ and 50% sand.  Tagro (http://www.tagro.com/) also has some products that would work as well.  If you have enough of your own soil use Tagro’s potting soil mix which contains no sand.  It is 20 percent Tacoma biosolids, 20 percent high-quality maple sawdust and 60 percent clean, aged bark. If you do not have enough existing soil to use Tagro mix which contains 50 percent biosolids, 25 percent sawdust and 25 percent screened sand. 

-- HG

Q. Hi Peter, I’d like to put a border around my approximately 40′X 40′ vegetable garden. Railroad ties would work nicely but I’m concerned about them leaching toxic chemicals into the soil and thereby ending up on my dinner table cleverly disguised as my awesome Super-Jubilee corn or Brandywine tomatoes. Are R/R ties a no-no around the garden? What would you suggest? Thanks Again, Henry Raynor - Puyallup, WA

A. Growing veggies in raised beds is a great idea.  Raised beds generally warm up and dry out quicker in the spring, which means you can get a jump-start on those early crops.  Also most gardeners do not walk in the raised beds, which means the soil is not damaged by compaction.  You are very wise to be concerned about what you use to make the raised beds.  Many gardeners that build raised beds may be tempted to used pressure treated wood.  This makes sense from the standpoint of longevity of the wood.  Treatment of wood with chemicals like creosote or chromated copper arsenate [CCA] slows down rotting of wood from soil microorganisms and insects like termites.  Unfortunately when used near vegetable gardens is that as you suspect there can be leaching of these chemicals which can find their way into your vegetables and then inside you.  Advocates of CCA pressure treated wood would tell you that the risk of contamination is low. So it is a risk benefit situation and everyone has to decide what he or she is comfortable with.  The EPA maintains that treated lumber should only be used for outdoor structures.  My sentiment is why take the risk when there are other options.  I simply used untreated wood on my beds knowing I will have to replace them in 3-5 years.  If you want longer lasting raised beds you could invest in naturally rot resistant woods like redwood or cedar.  There is also plastic lumber made from recycled plastic which is UV protected.  Unfortunately in the timber rich PNW plastic lumber has not, in my experience, been easy to find. 

-- HG

Q. I planted some peonies back six or seven years ago which still haven’t bloomed.  They get plenty of sunlight - what could be the problem and can I fix it at this point. Rhonda Moore - Wynnewood, Oklahoma

A. Well first off we can rule out age as being a factor.  Peonies grown under ideal conditions would have bloomed within the first couple or three years.  I am assuming you haven’t moved these peonies since this could set them back and delay blooming.  Second we can rule out sunlight as long as your idea of plenty of sunlight is the same as the peonies’ requirement for sunlight. Plants can get sufficient sunlight to sustain themselves but not enough to give them the extra energy required to bloom and set seeds. Be sure they are getting full sun for the majority of the day.  Planting depth can also be an issue with peonies.  The “eyes” of the plant (the overwintering below ground buds, think potato eyes) should have be around 2 inches below the soil line when you planted them.  If they are too deep the plants won’t flower.  If the plants settled or you put a lot of mulch on top of them this can also cause the eyes to sit lower.  The reverse of this, planting to shallow, can mean that buds are damaged by winter cold destroying the flower buds that were formed.  New vegetative buds can and do replace them but the result is lack of blooms.  Now is a good time to carefully move some soil away from the crown and see how deep the eyes are.  You can lift them and replant them to the proper depth once the soil can be worked.  Excessive nitrogen fertilization has also been mentioned as a factor in lack of blooms.  The theory is that the nitrogen promotes foliage and keeps the plant in a more juvenile state.

-- HG

Q. I would like schedule of month-to-month lawn care starting now. Thanks, Joe Miller - Puyallup, WA

A. Laying out a maintenance schedule for you would be more than I can fit in this column so I am going to refer you to a publication from Oregon State University titled Maintaining a Healthy Lawn in Western Oregon.  Washington State University doesn’t have a publication with this kind of month-to-month data.  Since the conditions of Western Oregon are quite similar to Western Washington this pamphlet can be used without alteration.  It provides information on how many times (on average) you should mow each month, water each month (inches per week) as well as fertilization schedules and thatching times.  This is a great starting point if you are new to taking care of a lawn but you should not use these as guidelines and starting points to get you started.  Nothing can substitute for your own observation of lawn height (tells you when to mow), natural rainfall (tells you how much supplemental water to provide) and soil testing (tells you when and how much fertilizer to apply).  Hopefully you are a regular reader and have seen some of the other lawn questions I have answered on moss control, de-thatching, et. al.   Here is a link for the publication online:

 http://eesc.orst.edu/agcomwebfile/edmat/html/EC/EC1521/EC1521.html

-- HG

Q. When is it safe to plant bleeding heart .I received a plant but know nothing about when I can put it in my garden. Thank you for any advice you can give me.  Christina Mulac - Louisville, Kentucky

A.  Bleeding Heart (Dicentra spectabilis) is a hardy perennial in the continental US.  Hardy means it can survive the coldest temperatures in the winter and perennial means it comes up multiple years (as in perennially).  Like other hardy perennials they can be sown in the spring or in the fall.  If you bought the plants as dormant roots then plant them as soon as you can work the soil.  This means waiting until frost leaves the soil and the soil dries out sufficiently.  This prevents damage to the soil structure.  To tell if the soil has dried out sufficiently take a hand full and squeeze it together lightly into a ball.  Then drop it to the soil surface from about 18 inches.  If the ball breaks apart the soil is dry enough to work.  If it stays in a firm ball then you should wait.  If the plant is grown in a container it can also be planted as soon as the soil is ready except if the plant was grown in a protected structure, like an greenhouse or coldframe.  If it was bought at a garden center you can ask them if the plant has been outdoors unprotected for at least two weeks.  If so then plant away! Bleeding heart prefers a partly shady spot - especially when grown in an area with hot summers like you can get in Louisville. 

-- HG